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Intermittent starting issue... (Solved)


mysterylemon
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Hi,

Got an intermittent starting issue with my 1.4 16v Lupo.

95% of the time it starts perfect on the turn of the key. It runs and drives perfectly with no other issues. the 5% of the time that it wont start on the key, it just turns over without even trying to start. You could sit there until the battery runs out with the engine spinning. It just wont start.

At first, I would take the key out and put it back in. This would usually solve the problem but sometimes would take 5 or so attempts for it to fire as normal and then it would litterally start perfectly on the key after not firing for 5 attempts. This lead me to think it may be an immobiliser issue but I have found that when it wont start, if you pump the throttle, it does eventually start (after about 10 seconds of pumping). It then idles erratically for around 10 seconds and then settles into a perfect idle and drives perfectly too.

It's totally random. Can't work out any sort of pattern or even guess at when it will do it... It can do it first thing in the morning from cold or after a long run when warm.

I've ruled out the immobiliser in my head now but no idea what to look at next... I get no errors or warning lights when it wont start so can anyone point me in the right direction?

Cheers!

Edited by mysterylemon
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For an intermittent fault like that mate I'd have to suggest getting a code reader on it, you can't really rule out an immobiliser fault based on what I've read here.

Saying that there could be several causes for this fault but without some kinda diagnosis of stored/current faults and sensor readings you may just go round and round in circles.

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Cheers for the replies!

Luckily I do have a OBDII cable so just downloaded Carport and read the codes.. Tried VCDS-Lite but to be honest, it was useless.

Found a few faults on a number of ECUs but the only that could be related are the following :

00282 Throttle valve positioner (V60)

Output open, intermittent

01176 Key

not authorized, intermittent

So this doesn't really point me in a specific direction. Could be immobiliser (although im not convinced) or could be related to the throttle valve position sensor although i'm not sure if this would cause the car not to start one minute and then start perfect the next... Any ideas?

I'm also still not convinced about the immobiliser as when it "wont" start, it will start if I pump the throttle pedal for 10 seconds or so. Surely if the immobliser wasn't letting the car start, it just wouldn't start at all? Plus going by what google says, I should be getting immobiliser errors on the dash if it didnt recognise the key.

Help :)

Edited by mysterylemon
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I dunno, I'd definitely go down the route of the immobiliser, it may not get its signal across to start with, then after a few seconds it picks it up.

The throttle positioner shouldn't make a difference whether the car starts up or not, as the car should fire up without the foot on the gas either way.

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The Immobiliser does seem to be the suspect but still strange that it can be started with some effort.

What does the Lupo Immobiliser immoblise? Fuel pump or ignition system?

Also, just been out to check but is there supposed to be an immobiliser light on the dash that lights up and goes out when you put the ignition on? If so, mine doesn't.

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Mine doesn't either, this has come up before, someone reckoned their immobiliser was fine because no key light or owt came on, not realising their instrument cluster wasn't fitted with one, and the immobilisers function is to stop the ignition process, the fuel pump will start working once the ignition is turned on.

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Ah right well thats fair enough. Just assumed it would as most cars do.

I have noticed that sometimes the fuel pump wont prime when turning the ignition on, although it seems to have no relation to whether it will start or not. Plenty of times It has remained silent and still started fine.

Google seems to suggest a common problem with VWs and the immobiliser reader coil thingy around the ignition barrel.. although I found nothing relating directly to the Lupo. Is this a common issue with the Lupo too? Loose/dodgy connection etc.

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OK, just so I know for sure, did you have two keys originally and just decided to replace one of them for some reason, or did you have one key and bought a blank one off ebay or somewhere like that and then get the blade of it cut to the same pattern as your only key? If so the one you got off ebay, unless specified, will not have a transponder chip fitted in it, so it'll work while the other key is near it, but it'll soon cut out when it loses the signal from the other key with the chip in it.

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Haha! Sorry dude, didn't know they could do it so cheap, is it an old school type key? Does it work your central locking or just a blank fob? Probably where I'm getting confused.

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groovy, well thats cleared that up then, if the fault occurs with both keys, which im almost certain it will do at some near point, then it will point towards your immobiliser.

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In my experience the immobiliser starts the engine and the stops it after a few seconds

Once dropped the transponder out of my GTI key whilst changing the battery, took me freaking ages to figure that one out I tell you!

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I've never had this Defcon, the only time it's happened like that to me was when I had another key cut, as the OP, but didn't even give a thought to the chip and i had the original key next to it, on the dash, and then it shook off and fell in the footwell and the engine cut out, all other times the engine cranks and cranks and cranks its been down an immobiliser fault, I guess we'll soon find out matey!

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I just don't understand that it will just crank and crank but will start if you pump the throttle. Surely it wouldn't if the immobiliser was cutting the ignition? But then it also seems that if you take the key in and out a few times it will start perfectly too...

Edited by mysterylemon
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